1. Field of the Invention
The present invention relates to a hose for transmitting a fluid under pressure, and more particularly to a hose for and a method of attenuating a fluid pressure pulsations produced in a pressurized-oil piping, a gas piping and like pipings employed in construction equipments, construction vehicles and further industrial machines.
2. Description of the Prior Art
In case that a liquid such as oil and water or a gas such as air and the like is transmitted under pressure through pipes, such fluid is generally transmitted together with its periodic pressure pulsations which cause objectionable vibrations in the pipes. These vibrations propagate throughout the entire piping of the pipes to produce a noise, and further, at worst, to cause breakage of at least a part of the piping.
In order to prevent such noise and breakage from occurring, hitherto employed are a fluid wave motion attenuating device of a so-called quincke-filter type and that of a so-called quarter-wave side-branch type as shown in FIGS. 1 and 2 of U.S. Pat. No 3,323,305, respectively. In any of the above conventional devices, a main conduit portion thereof is coupled with a side-branch portion in the fluid in which is produced a different-phase pressure wave being out of phase with respect to a pressure wave passing through the fluid in the main conduit portion, so as to make these pressure waves interfere with each other to attenuate the periodic pressure pulsations of the fluid in the main conduit portion of the device.
However, in any of these conventional attenuating devices, since the side-branch portion is coupled with the main conduit portion in a close-ended branching manner, the device is excessively large in size. In addition, in case that one of the conventional attenuating devices is provided with a main conduit portion in the fluid in which, for example, a pressure wave having a frequency of 300 Hz is produced, such main conduit portion must be coupled with a side-branch portion having a length of approximately 1 m to conduct an effective attenuation of the pressure wave of the fluid, a top-end part of which side-branch portion must be, therefore, fixed to a certain mount body. As a result, the objectionable vibrations are transmitted from the top-end part of the side-branch portion of the attenuating device to such certain mount body. These are defects inherent in the conventional devices.
In order to resolve these problems inherent in the conventional fluid pressure wave attenuating devices, the above U.S. Pat. No. 3,323,305 further discloses improvements in the fluid pressure wave interference type attenuating devices of both of the quincke-filter type and the quarter-wave side-branch type, as shown in FIGS. 6 and 7 thereof, respectively. In these improved conventional devices, the side-branch portion is coaxially mounted on an outer periphery of the main conduit portion thereof to make it possible to construct the devices in an appearance-refining manner and a size-saving manner.
However, in these improvement of the conventional devices, since the side-branch portion is connected with the main conduit portion thereof in a loose manner while not positively defined against the latter, there is a problem in that an appropriate phase difference is not necessarily produced between a periodic pressure wave produced in the fluid in the side-branch portion and that produced in the fluid in the main conduit portion to make it impossible to cause an effective interference between these fluid periodic pressure waves.